If I put a ring circuit for sockets in the loft, where can the "ring" start ? If back to the fuse box, there will be both sides of the ring running side by side all the way from the loft to the fuse box, before they diverge in opposite directions to form the ring. Is this the usual way to do it ? Cheers, Simon.
Yes, You may* be able to run a single 4mm cable from the consumer unit, to a suitable junction box, then create your ring from and then back to there - but I doubt it is worth the bother!
*I don't know if this is permitted, I am sure others will clarify
That's fine, I want to run wires through a bathroom stud wall I am creating, for future use. I will prob run 3 x TWE 2.5mm to allow ring and lighting circuits in the future. Simon.
If this is in the loft, as you say, and you don't expect it to be used a lot, you can run a radial if you wish.
Start at the CU (with a 16A MCB) using 2.5mm cable, then just string all your sockets to this as you wish (daisy chained and spurred (including spurs) The only down-side, is you are limited to a total load of 16A, not 32A as with a ring.
For example, this is permitted with a radial (but not a ring)
CU----Socket-----Socket-----Socket | | Socket Socket | Socket-----Socket-----Socket | Socket | Socket
...However, if you had that many sockets, then you would probably want to create more then one radial, or use a ring!
Sparks...
Thanks for the advice. Expect to do a loft conversion one day, so will put in something to cope with that. Simon.
Try to think of any other cables you may need in the future then, It wouldn't hurt to run.. Network Alarm Co-Ax (but you need to separate the mains from this as much as you can)
If you can run a couple of ducts, that may be useful too!
AIUI, it would be technically acceptable to run a lasso circuit. However, as it is not a standard circuit, you would have to do all the calculations to prove this. This is unlikely to be worthwhile. It is far more usual to use a standard ring circuit and run two cables back to the consumer unit, so that you can just use the tabulated maximum lengths in the OSG. Note that using
4mm to the lasso would likely give you worse maximum length than using 2 x 2.5mm.Further disadvantages of the lasso are that it might confuse others maintaining the system and it would be much more difficult to test. Ring circuits have a distinct advantage when it comes to testing over radials. The advantage over a lasso will likely be even greater, as you might need to do two tests, one of the ring section and one of the radial supply.
Christian.
Actually, to make this a standard socket circuit, it should be done with a
20A MCB. This should be enough for most loft conversions. In the worst case scenario, it gives you 600W on top of two 2kW fan heaters during a central heating failure.I can't be sure of the exact figure, but IIRC, the regs allow you 50m2 of floor space off a 20A radial socket circuit, with unlimited numbers of sockets. I believe the published floor space is concerned mostly about emergency backup heating requirements, given that the only other things plugged in are consumer electronics, which take almost no power, and the occasional vaccuum cleaner.
Christian.
The message from "Sparks" contains these words:
Is there a limit to how many sockets you can have on a radial?
On 21 Jul 2006 07:08:59 -0700 someone who may be "sm_jamieson" wrote this:-
Unless the loft conversion is very big then a standard 20A radial circuit will be fine for this and will save a fair amount of cable. There can be unlimited numbers of sockets on such a radial, provided it serves the appropriate floor area.
If the loft conversion is very big a 30/32A radial would often be a better choice than a 20A radial or a 30/32A ring.
Remember to allow for likely temperatures in your cable sizing.
No, but there is a limit to the amount of floor space it may serve. This is intended to cover the emergency use of electric heating when your primary heating system is inoperative.
Christian.
On Fri, 21 Jul 2006 16:35:36 +0100 someone who may be Guy King wrote this:-
Not on the types of radial one is most likely to see in houses and small commercial settings.
If the designer gets their calculations wrong then the circuit will not be able to supply the load and trip frequently. The maximum floor areas are designed to guard against this in typical buildings.
Why not a 20A MCB if it uses 2.5mm?
My Bad, 20A is what I should have put - I blame the heat!
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